Lab

Blood Urea Nitrogen

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Blood Urea Nitrogen, BUN

  • Pathophysiology
  1. Increases by 10-20 mg/dl/day if Renal Function absent
  2. Serum Creatinine is a better measure of Renal Function
    1. BUN is Protein dependent
      1. High protein diet
      2. Catabolism
    2. BUN is reabsorbed at renal tubules
      1. Prerenal Failure
        1. Dehydration
        2. Congestive Heart Failure
      2. Postrenal Failure
        1. Obstructive Uropathy
  • Increased BUN
  1. Medications
    1. Aminoglycosides
    2. Diuretics
    3. Lithium
    4. Corticosteroids
  2. Dehydration
  3. Gastrointestinal Bleeding
  4. Decreased Renal Blood Flow
    1. Shock
    2. Congestive Heart Failure
    3. Myocardial Infarction
  5. Renal disease
    1. Glomerulonephritis
    2. Pyelonephritis
    3. Diabetic Nephropathy
  6. Urinary Tract Obstruction
  • Decreased BUN
  1. Liver disease
  2. Poor nutrition
  3. Overhydration
  4. Third trimester of pregnancy